🎲 Dice Expectation and Probabilities in Craps

 

✅ What Is Dice Expectation?

Expectation (or expected value) is a mathematical concept that tells us the average result we can expect from a random event over time. In the case of dice, it’s the average value you would get if you rolled the dice thousands or millions of times.

For One Die:

  • Possible outcomes: 1, 2, 3, 4, 5, 6
  • Each has an equal probability: 16\frac{1}{6}
  • Expected Value (EV) = 1+2+3+4+5+66=3.5\frac{1 + 2 + 3 + 4 + 5 + 6}{6} = 3.5

For Two Dice (Used in Craps):

  • Possible sums: 2 through 12
  • Total combinations: 36 (6 sides × 6 sides)
  • Some sums are more likely than others. For example:
  • 7 can be rolled in 6 ways (e.g., 1+6, 2+5, 3+4, etc.)
  • 2 or 12 only in 1 way each (1+1 or 6+6)

So, the expected value for a roll of two dice is:

That’s the average result you'd see over many rolls.


🎯 Probability Breakdown (Craps Focused)

Sum Combinations Probability
2 1 (1+1) 1/36 ≈ 2.78%
3 2 2/36 ≈ 5.56%
4 3 3/36 ≈ 8.33%
5 4 4/36 ≈ 11.11%
6 5 5/36 ≈ 13.89%
7 6 6/36 ≈ 16.67%
8 5 5/36 ≈ 13.89%
9 4 4/36 ≈ 11.11%
10 3 3/36 ≈ 8.33%
11 2 2/36 ≈ 5.56%
12 1 (6+6) 1/36 ≈ 2.78%

These probabilities form the foundation of craps — the rules and payouts are structured around them.


🧠 Conclusion: Do Dice Perform as Theory Predicts?

Yes — in the long run, dice perform very closely to what theory and probability predict. Here’s why:

  • Randomness: Properly made and rolled dice are fair, meaning each side has an equal chance of landing.
  • Law of Large Numbers: Over many rolls, the actual outcomes converge to the theoretical probabilities.
  • For example, if you roll dice 36,000 times, you’ll see a 7 appear close to 6,000 times (about 16.67%).

Real-World Note:

Short-term deviations (like rolling a 7 five times in a row) are normal and expected in randomness — but over time, these balance out.


✅ Summary

  • Dice expectation tells us what outcome we should expect on average.
  • In craps, the most common total is 7, with an expected value of 7 for two dice.
  • The probabilities of each dice combination are known and consistent.
  • Over time, real dice rolls closely match theoretical expectations, confirming the reliability of mathematical models in games of chance like craps.

For more info visit https://www.4dcraps.com

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